Cut-off and slotting insert having cutting edges on four symmetrical corners

ABSTRACT

In order to improve cutting insert economy with simplified manufacture, an exchangeable insert (1) is configured generally symmetrical in the form of a four-cornered plate with four cutting edges (4) in the corners respectively and with plane-parallel abutment surfaces (5) disposed between the cutting edge portions and at right angles to each other. All of the cutting edge portions are mutually identical to each other, and each cutting edge portion is symmetrically formed about a bisector which passes through a circular center hole in the insert. This is provided in order to achieve a high degree of accuracy with respect to position and direction when attaching the cutting insert to the holder (3). Manufacture of the cutting insert is simplified considerably by gathering several insert blanks into a pack and first grinding the blanks simultaneously to their correct external shape and then fitting each insert-blank in a fixture in a diamond pattern, in which the edges of each insert-blank can be ground individually to its intended form.

The present invention relates to an exchangeable cutting insert and alsoto an insert holder, for slotting and parting-off a workpiece, forinstance for parting-off a workpiece with the aid of automaticallycontrolled workpiece processing machine.

TECHNICAL FIELD

A workpiece can be slotted and parted-off in various ways, for instanceeither plastically or mechanically with the aid of cutting inserts.Parting-off is achieved by cutting material from a rotating workpiecewith the aid of a cutting insert, such as an appropriate indexableinsert clamped in a holder intended therefor. Products can be producedquickly d efficiently in modern day NC and CNC lathes/machiningappliances fitted with cutting inserts and insert, holders. Parting-offof a workpiece is effected in a manner corresponding to a normal latheturning operation, in which the cutting bit, or lathe tool, is fedinwards after each revolution of the work-piece through a distance whichis equal to the thickness of the chip or swarf removed. The cutting tipof an indexable insert is normally ground to the width that iscorresponded, for instance, between two flanks.

Exchangeable bits or cutting inserts for slotting and parting-offworkpieces have been available commercially since the beginning of the1960's. There have been used mostly three-edged inserts which have beensecured in an upstanding position in an insert-attachment provided in aholder therefor. In conjunction with the development of machiningapparatus and appliances, it has been necessary to incorporate greatersafety measures against the breakage or fracture of cutting inserts inthe performance of their work, particularly in the case of unmanned,continuously working machines. Because of the high investment costsinvolved with large machines of this kind, necessary at present time,the economics of such cutting inserts, or bits, have become increasinglyimportant to the companies concerned.

SUMMARY OF THE INVENTION

With the intention of improving cutting insert economy in conjunctionwith simplified manufacture, the inventive exchangeable insert has beenconfigured generally symmetrical in the form of a four-cornered platewith four cutting edges in each corner and with plane-parallel abutmentsurfaces on each edge-side. These abutment surfaces are disposed betweenthe cutting edges perpendicularly to one another, which results in ahigh degree of accuracy with respect to position and direction whenattaching the cutting insert to the holder. The shape of the cuttinginsert allows it to be reversed and indexed, and allows narrowtolerances to be used. Manufacture of the cutting insert can besimplified considerably, by gathering several insert blanks together toform a pack and first grinding the blanks, all at once, to their correctintended external shape and then fitting each insert-blank in a fixturein a diamond configuration, in which the edges of each insert-blank canground to its intended form. Because the cutting insert is placed on oneedge, the insert will have a high mechanical strength. The cuttingforces will act on the corners of the cutting insert within a largeangular range and will be taken-up essentially by the whole of theinsert, thereby greatly reducing the risk of the insert fracturing. Oneand the same cutting insert can be used both for right-hand andleft-hand use.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, B, and C respectively illustrate an inventive cutting insertfrom above, from one side and at right angles to a diagonal.

FIGS. 2A, B show the insert fitted to an insert holder.

FIG. 3A shows the insert fitted to a grinding fixture.

FIG. 3B is a side view of a ground profile for an insert fitted to afixture.

FIG. 4 shows one end of an insert bundle and a ground profile.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 illustrates a possible configuration of an exchangeable cuttinginsert 1 made of HSS or cemented carbide for slotting or parting-off aworkpiece, in accordance with the invention. The insert 1 is of theindexable kind and is essentially square in shape, with centrallypositioned hole 2 by means of which the insert 1 can be fitted to aninsert holder 3 (see FIG. 2). Each corner of the insert 1 is providedwith an outwardly protruding and bevelled cutting edge portion 4 havingan edge 18. Mutually opposing side edges 5 of the insert 1 are disposedin pairs, parallel with one another. The cutting edges 4 extend outwardsfrom the center. The pairs of mutually opposite abutment surfaces 5 areused as abutment surfaces when fitting the insert 1 to the holder 3 andare mutually perpendicular to one another, therewith assisting inaccurate positioning of the insert 1 in the holder 3, said holder havingcorresponding mutually perpendicular surfaces with intermediate spacingfor accommodating a cutting edge 4 on one or both sides. The attachmenthole 2 may be bevelled or chamfered, as at 6, on one or both sidesthereof, which together with an appropriate attachment device 7 assistsin providing firm fixture of the insert 1 to the holder 3 and alsoenables the insert to be indexed and re-fixed to the holder, whennecessary. The insert is provided forwardly of each cutting edge portion4 with a chip-breaker or chip-leader 8, for instance a narrowing bevelon each of the respective side edges 5 forming an angle, illustrated at12, of about 15° relative to the respective side edge 5. The insert 1 isheld in the holder in an upstanding position and inclined at an angle ofabout 9°, with the aid of an appropriate fastener. There is obtainedwith this type of cutting insert and the manner in which it is held inthe holder 3 a favourable distribution of cutting forces throughout theinsert, said forces acting essentially in the plane of the insert,towards its center, therewith reducing the risk of insert fracture.Together with the cutting edges of the insert, the corners of the inserttake up a large angular range which also results in favourabledistribution of the cutting force acting on the insert and also infavourable heat distribution in the cutting edge portions.

FIG. 4 is an end view of a bundle or pack 9 of cutting inserts andillustrates a conceivable corresponding profiled grinding tool 10. Thisgrinding tool can be passed backwards and forwards over the pack in amanner to produce planar abutment surfaces 5 and bevelled cutting edges4, 8. The corners of the insert are bevelled, in order to provide goodcutting properties, for instances when machining workpieces of smalldiameters, and also to provide an efficient chip-breaking/chip-leadingeffect.

FIGS. 3A and 3B illustrate several cutting inserts taken from a groundpack of insert fitted to a fixture at equally large center distances. Inthis case, a second grinding tool 11 can be passed backwards andforwards over several inserts disposed diagonally and in line with oneanother, so as to produce the desired profile on the planar cuttingsurfaces, thereby minimizing the number total number of grindingoperations required. A widening bevel on each of the planar sides 14forming an angle, illustrated at 13, of about 4° relative to therespective planar side 14 will provide the cutting edges with goodcutting properties.

Because the square located area inwardly of ground regions of the insertis thicker than the remainder of the insert, compensation is obtainedfor the presence of the attachment hole and this thicker area will alsoafford good resistance to torque when the cutting insert is in use.

The number of grinding operations required to produce a cutting insertof the aforedescribed kind is greatly reduced by the present inventionwhile, at the same time, there is obtained an indexable cutting insertwhich has four cutting edges, these features contributing towardsachieving good insert economy, both with regard to insert manufactureand use of the insert.

All of the cutting edge portions 4 are mutually identical, and eachcutting edge portion 4 is symmetrically formed about a bisector orbisecting line, illustrated at 15, which passes through the center ofthe insert 1 wherein the cutting insert 1 can be fitted alternatively tothe right or to the left side of the holder 3 for right-hand orleft-hand use. The insert is characterized in that each cutting edgeportion 4 is shaped as a projection at the related corner of the insert1 and forms an acute angle, illustrated at 16, at its edge, illustratedat 18, so that each abutment surface 5 is located inwardly offset from aline, illustrated at 17, connecting the cutting edges 18 at each end ofthe abutment surface 5. Angle 16 is preferably about 60°.

I claim:
 1. An exchangeable, indexable generally four-sided slotting andparting-off cutting insert which has a pair of planar sides and fourside edges and which has a cutting edge portion having a cutting edgeprovided at each corner thereof and which includes mutually parallel andmutually opposing planar abutment surfaces between the cutting edgeportions and which further includes a circular center hole for fittingthe insert to a holder in an upstanding position and for holding saidinsert in said holder characterized in that all of said cutting edgeportions (4) are mutually identical, and each of said cutting edgeportions is symmetrically formed about a bisector which passes throughthe center of the circular center hole and said respective cutting edgeportion; and in that each cutting edge portion (4) has means defining anarrowing bevel adjacent the side edge, each bevel forming an acuteangle relative to said respective side edge, and the planar sidesforming a widening bevel at an acute angle relative to said respectiveplanar side, wherein a thickness of the insert increases toward theabutment surfaces.
 2. A slotting and parting-off insert according toclaim 1, characterized in that said narrowing bevel angle (12) is about15°.
 3. A slotting and parting-off insert according to claim 1,characterized in that said widening bevel angle is about 4°.
 4. Anexchangeable, indexable generally four-sided slotting and parting-offcutting insert (1) which has a pair of planar sides and four side edgesand which has a cutting edge portion (4) having a cutting edge (18)provided at each corner thereof and which includes mutually parallel andmutually opposing planar abutment surfaces (5) between the cutting edgeportions (4) and which further includes a circular center hole (2) forfitting the insert to a holder (3) in an upstanding position and forholding said insert (1) in said holder (3) all of said cutting edgeportions (4) being mutually identical, and each of said cutting edgeportions (4) being symmetrically formed about a bisector (15) whichpasses through the center of the circular center hole (2) and saidrespective cutting edge portion and having means defining a wideningbevel on the planar sides which forms an acute angle relative to saidrespective planar side; wherein a thickness of the insert increasestoward the abutment surfaces, characterized in that each cutting edgeportion (4) is shaped as a projection of the insert having a narrowingbevel (1) forming an acute angle (16) adjacent each cutting edge (18) sothat each abutment surface (5) is located inwardly offset from a line(17) connecting the cutting edges (18) at each end of the abutmentsurface (5).
 5. A slotting and parting-off insert according to claim 4,characterized in that said acute angle (16) is about 60°.
 6. A slottingand parting-off insert according to claim 4, characterized in that saidwidening bevel angle is about 4°.
 7. A slotting and parting-off insertaccording to claim 4, characterized in that the insert has meansdefining a narrowing bevel on the side edges which forms an angle (12)relative to said respective side edge.
 8. An exchangeable, indexablegenerally four-sided slotting and parting-off cutting insert (1) whichhas a pair of planar sides and four side edges and which has a cuttingedge portion (4) having a cutting edge (18) provided at each cornerthereof and which includes mutually parallel and mutually opposingplanar abutment surfaces (5) between the cutting edge portions (4) andwhich further includes a circular center hole (2) for fitting the insertto a holder (3) in an upstanding position and for holding said insert(1) in said holder (3); all of said cutting edge portions (4) beingmutually identical, and each of said cutting edge portions (4) beingsymmetrically formed about a bisector (15) which passes through thecenter of the circular center hole (2) and said respective cutting edgeportions and having means defining a widening bevel on the planar sideswhich forms an acute angle relative to said respective planar sidewherein a thickness of the insert increases toward the abutmentsurfaces; characterized in that each cutting edge portion (4) is shapedas a projection of the insert (1) forming an acute angle (16) adjacenteach cutting edge (18) so that each abutment surface (5) is locatedinwardly offset from a line (17) connecting the cutting edges (18) ateach end of the abutment surface (5), the insert having means defining anarrowing bevel on the side edges which forms an angle (12) of about 15°relative to said respective side edge.